Can a lipoma swell up and down often without any pain?its on top of the bone at top of spine/base of neck and coz of it position it gets aggravated.

Yes it can: A lipoma is a benign medical condition. It can change the size up or down without pain. There is no need for a treatment. However, if the lipoma concerns you, is painful, infected or is growing, you may want to have it removed and biopsied.

Same size: A lipoma shouldn't fluctuate in size unless there is associated intermittent bleeding or fluid collection within it that comes and goes. Cysts and abscesses which are not solid growths, may fluctuate in size.

Not commonly: As typically lipoma if going to change in size, grow slowly in size. If it is changing in size more rapidly on the order of days to weeks, It's more likely a cyst of some sort. But I make sure your doc knows about it just do that someone is keeping an eye on it.